This invention is related to autonomic computing architectures using high reliability memory subsystems. Autonomic computing architectures using high reliability memory subsystems often employ redundant memory devices and an error correcting code, (ECC) to correct errors that occur during operation. The ECC can be structured with a multi-bit symbol to correct errors that result from an inoperative memory device. This is often referred to as ‘chip kill ECC’. A very high percentage of memory subsystem circuitry is typically covered through this means of error correction. Memory subsystems that utilize another high reliability feature called ‘sparing’ or ‘redundant bit steering’ are able to disable selected memory devices and replace them with dedicated spare devices allowing the memory subsystem to be repaired, or healed. Usually, the data path interconnections between the memory subsystem devices and ECC logic are also protected by this same mechanism.
Even with the above-mentioned high reliability features, inoperative circuits and interconnections that can result in uncorrectable errors still exist in memory subsystems. The majority of the remaining interconnection errors are typically found in the command and address signals within the memory subsystem. Because they are interconnected to multiple memory devices, a single inoperative circuit on a command or address bus, can result in multi-data bit errors.
Other high reliability memory subsystem architectures such as memory mirroring or raid-like redundant subsystem architectures use many additional memory devices to achieve higher reliability. This can add significantly to the cost of memory subsystems.
Therefore, what is needed in the art is a low cost solution that provides memory subsystem command and address bus redundancy between the dual inline memory module (DIMM) register and dynamic random access memory (DRAM) devices without adding additional redundant memory devices, to efficiently enable autonomic computing through additional self healing capabilities at reasonable prices.